Wallen's boyfriend, Tyler Tessier, was arrested Wednesday afternoon and charged with murder in her death.

In the days since Sept. 5, when the high school teacher failed to show up to work, Wallan's family, community, and — most notably — Tessier rallied behind authorities working to find the mom-to-be.

Tessier was with Wallen's parents as they spoke at a news conference Monday and announced a $25,000 reward for information leading to her return.

Tessier held the parents' hands and cried while giving his own brief statement.

But police now believe he killed Wallan and buried her in a shallow grave near Damascus, Md.

Tom Manger, Chief of Montgomery County Police, said at a news conference Wednesday night that Tessier has provided investigators with evidence suggesting his involvement and that it was determined he drove Wallen's car and removed its front tag.

Tessier also texted an acquaintance asking for a ride to Baltimore and help to "clean up a mess," which the acquaintance declined to do, Manger said.

A vigil was scheduled for Wednesday night but was canceled as the news of her murder emerged.

Instead, current and former students from Wilde Lake High School gathered with others at Wilde Lake Interfaith Center in Columbia to share their grief.

"It's unreal. It's like one of them bad Lifetime movies that you just like yeah I know what's going to happen in the next five minutes of the movie, like it's not real," one speaker said.

A student who knew Wallan described her as a teacher who went above and beyond for the good of her pupils.

"She's influenced us to be better in life," the student said. "Not just in school — in life."